Experimental study on localization of absorbers within tissue phantom using a simple phased-array system

A simple phased-array system with two anti-phased near infrared (NIR) light sources whose intensities are modulated sinusoidally at 200 MHz is established, and experiments for exploring the light distribution in a homogeneous tissue phantom (0.25% intralipid) and the perturbations of intensity null and phase transition by absorbers are carried out. Experimental results in this paper show regular light intensity null and sharp phase transition of 180/spl deg/ at the mid-line of the two sources, conform closely with the prediction by diffusion theory and the results of other groups. The authors' measurements clearly demonstrate the distortion of the light distribution by the existence of absorbers and the effects on the perturbations caused by different sizes and locations of the objects. The effect on the objects resolution of the spacing of the two light sources is also investigated and the authors found that higher resolution may be achieved by narrower spacing. Particularly, they have studied the possibility of distinguishing between two absorbers and have given initial results. It is concluded that phased-array system could be simple, feasible, and effective for small absorber discrimination in otherwise homogenous body tissues.